Gramophone tone-arm positioning mechanism



J. A. LEE

March 29, 1960 GRAMOPHONE TONE-ARM POSITIONING MECHANISM Filed Jan. 15,1958 United States Patent GRAMOPHONE TONE-ARM POSITIONING MECHANISMJames Alexander Lee, Walthamstow, London, England,

assignor to The Plessey Company Limited, Ilford, England, a Britishcompany Application January 13, 1958, Serial No. 708,726

2 Claims. (Cl. 274-15) This invention relates to gramophone tone-armpositioning mechanism and is an improvement in or modification of theinvention described in co-pending patent application Serial No. 655,920by H. Da Costa assigned to the same company as the presentspecification.

When the device according to said co-pending applications is used foroperation with records of three different sizes, care must be taken tomake the inertia of the feeler member and of the parts actuated therebysmall, to reduce the risk that these elements when actuated by a recordof the intermediate size may, due to inertia action, move beyond theirappropriate position so as to place the tone-arm mistakenly in thestarting position corresponding to a large-size record.

According to the present invention a single feeler member, engaged byboth large-diameter and intermediate-diameter records is employed, butovershooting the intermediate position is prevented by a step whichrequires displacement in a direction substantially perpendicular to thatcausing the transition from the smalldiameter position to theintermediate-diameter position in order to permit the further transitionof the largediameter position.

Thus in the case of a control element rotatable about a vertical axis,an axial displacement is required on reaching the intermediate-diameterposition, to permit the further movement to the large-diameter position.

This axial displacement is preferably arranged to be effected by theweight of the record depressing the feeler arm with its shaft againstspring action. The amount of the displacement required is very small,thus reducing any inertia delays to a minimum.

An embodiment of the invention is illustrated in the accompanyingperspective drawing, in which Figs. 1 and 2 respectively show themechanism in the intermediatediameter position and in the large-diameterposition.

A stop member 1 having a flange 13 co-operates with a teasing leversimilarly as shown in the said-co-pending application to control, in aknown manner, the end of the tone-arm positioning movement. The stopmember 1 is mounted on a vertical shaft 2 which is rotatable in thegramophone base 4 and carries a flag-type feeler arm 5. In its normalposition prior to the release of a record this arm projects into thepath of 10 and 12" diameter records as they move individually down froma stack to the turntable 10 of the record changer, while the arm isclear of the path of the periphery of 7" diameter records. This arm isprovided with an inclined ramp surface a, whereby a record of 10" or 12"diameter moving to the turntable will swing the arm 5 about the axis ofshaft 2 in the direction of arrow x as long as the arm is free so tomove, and until it is clear of the edge of the record in question. Thisrotation of shaft 2 will turn the stop member 1, against a light returnspring 33, to its 10" or 12" position according to the diameter of therecord. A latch lever 8, formed with abutment shoulders 11 and 12,serves to retain the stop member 1 in this position until it is releasedin due course for the resetting of the mechice anism before the nextrecord of the stack is allowed to drop onto the turntable. This releaseis efiected in any convenient or conventional manner by an element 12 ofthe change-cycle mechanism of the record changer.

In order to prevent the feeler arm 5 and the stop 1 from overshootingthe 10" position and from thus setting the tone arm mistakenly for a 12"record when a 10 record drops onto the turntable, a stop pin 34 projectsdown from the gramophone base 4 into the path of an abutment edge 35 ofthe stop member 1 so as to normally prevent the latter from movingbeyond the 10" position shown in Fig. l, to the 12" position. In order,however, to allow such further movement when a 12" record is releasedfrom the stack, the shaft 2 with the stop member 1 is enabled to movedownwardly under the weight of the record against the action of a lightsupporting spring 36, sufliciently for the stop member 1 to clear theend of pin 34. Thus when a 12" record has been released from the stack,the stop member 1 is free to move, under the action of the feeler arm 5,to the 12" position illustrated in Fig. 2, since the weight of therecord still rests on the arm 5 to hold the shaft and stop memberdepressed when the latter passes the 10" position. When on the otherhand, a 10" record has been released, the weight of the record, even ifit has been sufi'lcient to depress the shaft and stop member, ceases toact when the 10" position is reached, whereupon the spring 36 will atonce lift the shaft to return the stop member 1 to its position forcooperation with stop pin 34. It will be appreciated that the pin 34 maybe arranged to arrest the rotation of the stop member 1 at a point somedistance beyond the 10" position but short of the 12" position. Thisprovides ample time for the spring 36 to render the stop pin effective,whereupon the spring 33 will immediately return the stop member as faras the 10" position stop 11 of the latch member 8 will permit. Ifdesired, however, a fixed auxiliary abutment 37 (Fig. 2) or the like maybe provided which prevents the shaft and stop member from downwardmovement up to a point at which the arm 5 is out of the reach of a 10"record.

What I claim is:

1. In a tone arm positioning mechanism for turntable gramophones thecombination of a feeler arm mounted on and rotatable with a verticalspindle, spring means biasing said feeler arm and spindle for rotationto a normal position in which the feeler arm extends near to the centreof the gramophone turntable, said feeler arm having a cam surface forco-operation with the edge of a record disc moving from a magazine tosaid turntable to move the arm, when engaged by such edge, about theaxis of said spindle from said normal position to one or both of twopredetermined further positions, according to the diameter of suchrecord, a stop member mounted for rotation with said spindle andselectively controlling the positioning of the gramophone tone arm tothree positions according to whether said feeler arm is in said normalposition or in one or in the other of said predetermined furtherpositions, and releasable retaining means terminating, until released,the return movement of said feeler arm and stop member under the actionof said spring means at that one of said two predetermined furtherpositions which is first reached in such return movement, mounting meansfor said spindle permitting the spindle to move axially as well asrotatably, resilient means normally retaining said spindle in arelatively high position when no record rests on the feeler member,abutment means fixed on said spindle, and a stationary limit stop memberso arranged and dimensioned as to co-operate when said spindle is insaid relatively high position, with said abutment means, for terminatingrotation of said spindle against the action of said spring means at aposition intermediate between said two pre- 3 determined furtherpositions,z but to be cletrofthe path of said abutment means and thuspermit rotation of said spindle against the action of said spring meansbeyond said intermediate position when, due to the weight of a record:resting onsaid feeler arm, said spindle is,=against the action of saidresilient means, depressed from said relatively high position; v

2. A combinationas claimed in claim 1, including an auxiliary stoppreventing downward movement of said spindle to clear saidlimitstopmember when said am is 10 between its normal position and theposition correspondin'gto that of said predetermined" furtherpositionswhich is first reached by rotary movement against the action of saidspring means.

References Cited in the file of this patent UNITED STATES PATENTS2,752,159 Bacher e June 26, 1956 FQREIGN PATENTS 382,276 Great Britain iOct. 17, 1932 770,094 Great Britain Mar. 13, 1957

